Control apparatus for the measurement and folding of flat workpieces

ABSTRACT

A control apparatus for use with a machine for folding a flat workpiece comprising a first detector and transmitter unit arranged to detect and measure a dimension of a travelling workpiece and transmit a signal whose value is representative of said dimension to a first memory store arranged to accept said signal, means for transferring at least part of said signal in the first memory store from said first store to a second memory store, and a second transmitter arranged to transmit to said second memory store a further and cumulative signal representative of the passage of said workpiece relative to a folding station, said second memory store being arranged to initiate a folding operation when the required length of workpiece has passed said folding station.

United States Patent CONTROL APPARATUS FOR THE MEASUREMENT AND FOLDINGOF FLAT WORKPIECES 8 Claims, 9 Drawing Figs.

US. Cl 270/80, 270/83 Int. Cl B65h 45/06 Field of Search 270/80, 81, 82,83, 84, 85

[56] References Cited UNlTED STATES PATENTS 2,374,779 5/1945 Preston270/81 3,363,897 1/1968 Northern et al. 270/84 Primary ExaminerRobert W.Michell Assistant Examiner-L. R. Oremland AnorneyBeveridge and De GrandiABSTRACT: A control apparatus for use with a machine for folding a flatworkpiece comprising a first detector and transmitter unit arranged todetect and measure a dimension of a travelling workpiece and transmit asignal whose value is representative of said dimension to a first memorystore arranged to accept said signal, means for transferring at leastpart of said signal in the first memory store from said first store to asecond memory store, and a second transmitter arranged to transmit tosaid second memory store a further and cumulative signal representativeof the passage of said workpiece relative to a folding station, saidsecond memory store being arranged to initiate a folding operation whenthe required length of workpiece has passed said folding station.

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INVENTORS DAVIDHEY a; GEOFFREY Lumen Grimm/cop CONTROL APPARATUS FOR THEMEASUREMENT AND FOLDING OF FLAT WORKPIECES The present invention isconcerned with the measurement and folding offlat workpieces.

According to the present invention a control apparatus for use with amachine for folding a flat workpiece comprises a first detector andtransmitter unit arranged to detect and measure a dimension of atravelling workpiece and transmit a signal whose value is representativeof said dimension to a first memory store arranged to accept saidsignal, means for transferring at least part of said signal in the firstmemory store from said first store to a second memory store, and asecond transmitter arranged to transmit to said second memory store afurther and cumulative signal representative of the passage of saidworkpiece relative to a folding station, said second memory store beingarranged to initiate a folding operation when the required length ofworkpiece has passed said folding station.

According to one preferred feature of the invention each of the firstand second memory stores is an electronic circuit and comprises at leastone storage capacitor, each storage capacitor being connected to itsassociated transmitter through a resistance, the arrangement thusforming a resistance-capacitor circuit.

The means for transferring at least part of the signal originally storedin the first memory store to the second memory store may comprise aswitch, arranged when in its closed position to connect the two storesin parallel, with or without the association of other circuit elementsto govern the ratio of said sharing.

According to a further embodiment of the invention a third memory storemay be provided together with means for dividin g and transferringthereto any remaining signal stored in said first memory store after theoriginal information has been transferred to the second memory store,whereby a further folding operation canv be initiated by said thirdstore for further folding of the workpiece.

According to another embodiment of the invention for initiating furtherfolding operations, a third memory store may be provided together withmeans for dividing the original information transferred from the firstmemory store between the second and third memory stores whereby furtherfolding operations can be initiated by said third memory store.

One object of the invention is to provide a simple, cheap and robustcontrol apparatus for use with a folding machine for folding flatworkpieces.

A further object of the invention is to provide a control apparatus foruse with a folding machine for giving an accurate fold by the adjustmentof a variable resistor as a capacitor supply voltage.

Other and further objects of the invention will become apparent byreference to the accompanying drawings wherein:

FIG. 1 is a schematic diagram of the control system of the invention;

FIG. 2 shows one preferred input circuit suitable for use with theinvention;

FIG. 3 shows the resistance-capacitor circuit of the invention;

FIG. 4 shows one preferred output circuit suitable for use with thepresent invention;

FIG. 5 is a diagrammatic charge curve for DC charging of capacitor C1ofFIG. 3;

FIG. 6 is a diagrammatic charge curve for the DC charging of capacitorC2 of FIG. 3;

FIG. 7 is a schematic diagram of the folding operation;

FIG. 8 is a diagrammatic charge curve for both DC and pulsed chargingofa capacitor, and

ing partof a detector and transmitter unit 14 is arranged above conveyor10 the detector (not shown) being arranged for actuation by a travellingworkpiece 16 being carried along on the upper run of endless conveyorformed by the belts or tapes 10.

The transmitter 13 comprises a toothed wheel arranged for rotation bythe passage of a workpiece l6 therebeneath, the teeth of said toothedwheel being arranged to alternately interrupt and restore a light beamimpinging on a photoelectric cell 15. The output waveform of thisdetector is in the form of a spaced sawtooth voltage 17 which is thenfed to a first pulseshaping circuit 11.

One form of pulse-shaping circuit 11 which may be used is shown in FIG.2 and comprises a Schmitt trigger semiconductor circuit (shown on theleft of the FIG.) followed be a semiconductor monostable multivibrator(shown on the right of the FIG.) equipped with a resistance-capacitancedelay circuit arranged to set a constant pulse width.

The output waveform of this pulse-shaping circuit 11 comprises a trainof constant width, constant height pulses 19 supplied at a rateproportional to the velocity of the flat workpiece 16 as it drives thetoothed wheel of the unit 14. This train of pulses (shown schematicallyon FIG. 1 emerging from circuit 11) is delivered to the left-hand sideof the resistancecapacitance circuit Rl-Cl of the R-C circuit 21 of FIG.3 for the length of time that the detector associated with the unit 14is actuated. This detector, which may be in the form of a feeler switch,is connected so that operation thereof opens contact 18 (FIG. 3) thusallowing capacitor C1 of the circuit of FIG. 3 to become charged by saidtrain of pulses, as shown in FIG. 5. The charge acquired by'capacitor C1is thus proportional to the overall length of workpiece 16 becausecontact 18 is open for the full time that the workpiece is passing underthe detector of unit 14.

When workpiece 16 has completely passed the unit 14 the detectorassociated with the unit senses this fact and opens contact 20,simultaneously closing contact 22 (FIG. 3) momentarily. Thus a capacitorC2 connected in parallel to C1 acquires a part of the charge ofcapacitor C1.

Contact 18 then closes, and in so doing discharges capacitor C1 so thatthe circuit Rl-Cl is then ready for charging by any subsequent workpiecetravelling along the conveyor 10. Capacitor C2 is left holding atleastpart of the original charge of C1.

A second transmitter 24, (FIG. 1) similar to transmitter 13 is connectedto pulley wheel 28, over which the endless conveyor formed by belts ortapes 10 passes, by a rotatable shaft 26. Shaft 26 thus rotates at aspeed proportional to the velocity of workpiece 16 at any particulartime, After the workpiece 16 has passed beyond unit 14, the transmitter24 output voltage is fed cumulatively to capacitor C2 through resistanceR2 of the R-C circuit 21 via a second pulse-shaping circuit 30, whichcan be substantially the same as circuit 11 (FIG. 2).

The charge acquired by capacitor C2 from the second transmitter 24 isthus added to the charge stored on capacitor C2 from the previous chargetransfer from capacitor C1. When capacitor C2 has been charged to apredetermined firing voltage Vp (FIG. 6) the output circuit of FIG. 4conducts to produce an output causing the folding mechanism, indicatedschematically by folding blade 32, to operate. At the same time, contact20 closes to completely discharge capacitor C2 and thus prepare it forthe following cycle, when it will accept a further charge from capacitorC1 being built up thereon by the passage of a succeeding workpiecebeneath unit 14.

One preferred form of output circuit which may be used is shown in FIG.4. This circuit comprises a low leakage unijunction transistor 23 whichis used to provide an output pulse at the said firing voltage Vpfollowed by a thyristor 25 to give the required output signal to themachine for folding the workpiece.

By selecting suitable values for the time constants of circuits Rl-Cland R2-C2, for aiming voltage E1 and E2, and for firing voltage Vp(referred to hereafter with reference to FIG. 6) the system will enablefolding of the workpiece in any desired ratio regardless of the lengthof the workpiece fed to the device.

The theoretical aspect of the invention will now be further describedwith reference to FIGS. 5, 6, 7 and 8 of the accompanying drawings.

The charge curve of capacitor C1 is shown in FIG, 5. T is the timeconstant for the first memory store Rl-Cl, and E1 is the aiming voltageof capacitor C1. S1 is the workpiece velocity at the first detector andtransmitter unit 14.

The charge curve of capacitor C2 is shown in FIG. 6 in which E2 is theaiming voltage of capacitor C2 and Vp is that predetermined voltage atwhich capacitor C2 is arranged to discharge into the output circuit ofFIG. 4, Also T is the time constant for the second memory store R2-C2,and S is workpiece velocity at the second transmitter 24.

Referring now to FIG. 7 let x be the distance travelled by the workpieceafter measuring but before folding, and y be the length of the workpieceprotruding beyond the fold station then,

where l) is the distance between the unit 14 and fold station 32. and Lis the overall length of the workpiece. For half-way folding,

L/'l= Equations (1) and (2) give let r. be the time the workpiece takesto travel past the first transmitter, and I: be the time taken for theworkpiece to travel the distance x, then and it may be shown that forcapacitor C the charging voltage V=E (1e*' and from Equation (4) Thusfor capacitor C which gives 5 iEt- (ar W where equating Equations (5)and (6) and x=D- from Equation (3) if nE =E then Equation (9) may besimplified to give 1 82% a DS2Tg log 42 p L (9) if, for half-wayfolding,

SQTZ

then

D= 8; T log e :3. constant make D a constant, and satisfy the conditionsfor the workpiece to be folded in half.

The foregoing mathematical treatment of the invention assumes a DCcapacitor charging current, whereas in the particular description apulsed charging current was assumed. it is therefore necessary to showthe relationship between DC and pulsed charging currents.

Referring to FIG, 8 the curves for both DC and pulsed charging currentsare shown. The DC charging curve is shown as 44 and the pulsed chargingcurve as 46. Let t, be the time taken for the DC charging current tocharge a capacitor to voltage Vp., and let I, be the time for the pulsedcharging current to charge the same capacitor to voltage Vp. then, onthe pulse fed curve 46 I1=P(r1+r where P is the number of pulsesreceived (i.e. number of cycles) r is the time duration of the pulse(i.e. mark duration) r is the time duration before a subsequent pulse(i.e. space duration) and P=Lp where L is the length of the sheet to befolded p is the pulse rate but charging voltage V=E1(1 i/T|) for d.c.

and also V=E|(l e for pulsed current Lpr T1 now, if the mark-space ratiois 1/1, then r =rg and T,=2T but t1'=Lp(r +r2)=L/S, where S, is speedfactor S T =a constant S TQl' is independent of speed substituting inequation 10 S B/S T, is a constant and can be made equal to a half bysuitable selection of T T p and l From the foregoing it may thus be seenthat with the detector and switch set this distance D from the foldposition the circuit gives the required fold in any workpiece lengthwithin the range 0 L 3 2D In the above description it has been assumedthat the conveyor speed has not varied. If the conveyors travel at alltimes at a constant speed, then second transmitter 24 and pulseshapingcircuit 30 can be omitted and a constant DC voltage equivalent to thesecond pulse train previously mentioned can 'be fed into circuit Rl-C2when the workpiece has passed unit 14 and circuit Rl-CZ has received itsappropriate share of the charge from circuit Rl-Cl.

The description so far has been concerned with the provision ofa singlefold in workpiece 16. One method for obtaining second and subsequentfolds can be achieved by passing (10) the initially folded workpiecethrough the device and past the folding machine again. In such a casethe charge remaining on C1 after some of it has been transferred to C2,can be further shared through a suitable switching device, with anotheractuating circuit say R3-C3, similar to R2-C2.

A still further embodiment for initiating further folding operations isshown in FIG. 9 in which a resistance-capacitor circuit similar to thatshown in FIG. 3 is illustrated.

The difference between the circuit of FIG. 3 and that of FIG. 9basically resides in the fact that in FIG. 9 the second capacitor C2,and second resistor R2 are replaced by tow capacitors C2 and C3 and tworesistors R2 and R3 respectively.

The modes of operation of the two circuits are similar, inasmuch as thefirst capacitor becomes charged from the first detector and transmitterunit 14 (as hereinbefore described);

but the charge acquired by the first capacitor is shared between the twoadditional capacitors C2 and C3, which may be of equal capacity.

Additional capacitor C2 is firstly charged from the second transmitter24 and subsequently discharged into the output circuit of FIG. 4, bysuitable operation of switches 34, 36, 38, 40 and 42, thereby causingasignal to be issued to the folding machine to fold the workpiece once.

The capacitor C3 is then charged, either from the second transmitter,or, from a further transmitter associated with a further foldingmachine. Subsequently the capacitor C3 discharges into the outputcircuit of FIG. 4 thereby causing a further fold signal to be issuedwhich in turn causes the workpiece to be folded for a second time.

It is apparent that using the above-outlined procedure, any number offolds may be produced in a fiat workpiece.

In order flat successive workpieces travelling along the conveyor mayreadily be folded at different position along their length, it isenvisaged that either the resistors and/or capacitors of theresistance-capacitance circuit may be made variable.

We claim:

I. A control apparatus for use with a machine for folding a flatworkpiece at a folding station, the control apparatus comprising incombination, a first memory store, a first detector and transmitter unitarranged to detect and measure a dimension of a travelling workpiece andtransmit a signal whose value is representative of said dimension tosaid first memory store, said first detector and transmitter unitcomprising a photoelectric cell, a light source directing a light beamon said photoelectric cell, a toothed wheel, the teeth of which arearranged to alternately interrupt and restore impingement of said lightbeam on said photoelectric cell to create said signal at said photocell,means mounting said toothed wheel in cooperating relationship with aworkpiece the dimension of which isto be measured and which istravelling along a conveyor in said folding apparatus, means connectingsaid photoelectric cell and said first memory store to transmit saidsignal to said first memory store, a second memory store, means fortransferring at least part of the signal stored in said first memorystore to said second memory store and for subsequently releasing saidfirst memory store to receive subsequent signal from said first detectorand transmitter unit in response to measurement of a subsequenttravelling workpiece, and a second transmitter arranged to transmit tosaid second memory store a further and cumulative signal representativeof the passage of said first travelling workpiece relative to a foldingstation, said second memory store having means for initiating a foldingoperation of said folding apparatus when the required length ofworkpiece has passed the foldingstation.

2. A control apparatus according to claim 1 further including towpulse-shaping circuits each comprising a Schmitt trigger stage followedby a monostable multivibrator for producing a train of constant width,constant height pulses at a rate proportional to the velocity of thefiat workpiece, the output of said transmitter units being fed to saidpulse-shaping circuits respectively, and means respectively connectingsaid pulse-shaping circuits with said first and second memory store. 3.A control apparatus according to claim 1 wherein each of the first andsecond memory stores is an electronic circuit and comprises at least onestorage capacitor, each storage capacitor being connected to itsassociated transmitter through a resistance, the arrangement thusforming a resistance-capacitor circuit.

4. A control apparatus according to claim 1 wherein the means fortransferring at least part of the signal originally stored in the firstmemory store to the second memory store comprises a switch, arrangedwhen in its closed position to connect the tow stores in parallel, withor without the association of other circuit elements to govern the ratioof said storing.

5. A control apparatus according to claim 1 wherein a third memory storeis provided together with means for dividing or transferring anyremaining signal stored in said first memory store after the originalinformation has been transferred to the second memory store, whereby acan folding initiated be by said third store for further folding of theworkpiece. transmitting 6. A control apparatus according to claim 1wherein a third memory store is provided together with means fordividing the original information transferred from the first memorystore between the second and third memory stores whereby further foldingoperations can be initiated by said third memory store.

7. A control apparatus for use with a machine for folding a flatworkpiece which includes conveyor means for carrying a fiat workpiecebetween a sensing station and a folding station, the control apparatuscomprising, a detector and transmitter means including a feeler switch,a toothed wheel and a photocell for detecting and transmitting thelength of a workpiece as it travels on the conveyor means and fortransmitting a signal corresponding to the length of the workpiece, apulseshaping circuit means for receiving a signal from said detector andtransmitter means, and R-C memory storage means for receiving a signalfrom said pulse-shaping circuit means, a second capacitor, a switchmeans for transferring at least part of said signal from capacitor,first capacitor to said second capacitor, a second transmitter meansincluding rotatable shaft operatively connected to said conveyor meansto transmit to said second capacitor a further and cumulative signalcorresponding to part of the length of said workpiece after theworkpiece has left said sensing station, and means including said secondcapacitor for initiating a folding operation on the workpiece when theworkpiece is in proper position at the folding station.

8. A control apparatus as defined in claim 7 further including means fordischarging said first capacitor after said part of said signal istransferred from said first capacitor to said second capacitor forpermitting said first capacitor to receive subsequent signals from saidpulse-shaping circuit in response to the passage of a subsequentworkpiece by said sensing sta- IIOII.

1. A control apparatus for use with a machine for folding a flatworkpiece at a folding station, the control apparatus comprising incombination, a first memory store, a first detector and transmitter unitarranged to detect and measure a dimension of a travelling workpiece andtransmit a signal whose value is representative of said dimension tosaid first memory store, said first detector and transmitter unitcomprising a photoelectric cell, a light source directing a light beamon said photoelectric cell, a toothed wheel, the teeth of which arearranged to alternately interrupt and restore impingement of said lightbeam on said photoelectric cell to create said signal at said photocell,means mounting said toothed wheel in cooperating relationship with aworkpiece the dimension of which is to be measured and which istravelling along a conveyor in said folding apparatus, means connectingsaid photoelectric cell and said first memory store to transmit saidsignal to said first memory store, a second memory store, means fortransferring at least part of the signal stored in said first memorystore to said second memory store and for subsequently releasing saidfirst memory store to receive subsequent signal from said first detectorand transmitter unit in response to measurement of a subsequenttravelling workpiece, and a second transmitter arranged to transmit tosaid second memory store a further and cumulative signal representativeof the passage of said first travelling workpiece relative to a foldingstation, said second memory store having means for initiating a foldingoperation of said folding apparatus when the required length ofworkpiece has passed the folding station.
 2. A control apparatusaccording to claim 1 further including tow pulse-shaping circuits eachcomprising a Schmitt trigger stage followed by a monostablemultivibrator for producing a train of constant width, constant heightpulses at a rate proportional to the velocity of the flat workpiece, theoutput of said transmitter units being fed to said pulse-shapingcircuits respectively, and means respectively connecting saidpulse-shaping circuits with said first and second memory store.
 3. Acontrol apparatus according to claim 1 wherein each of the first andsecond memory stores is an electronic circuit and comprises at least onestorage capacitor, each storage capacitor being connected to itsassociated transmitter through a resistance, the arrangement thusforming a resistance-capacitor circuit.
 4. A control apparatus accordingto claim 1 wherein the means for transferring at least part of thesignal originally stored in the first memory store to the second memorystore comprises a switch, arranged when in its closed position toconnect the tow stores in parallel, with or without the association ofother circuit elements to govern the ratio of said storing.
 5. A controlapparatus according to claim 1 wherein a third memory store is providedtogether with means for dividing or transferring any remaining signalstored in said first memory store after the original information hasbeen transferred to the second memory store, whereby a can foldinginitiated be by said third store for further folding of the workpiece.transmitting
 6. A control apparatus according to claim 1 wherein a thirdmemory store is provided together with means for dividing the originalinformation transferred from the first memory store between the secondand third memory stores whereby further folding operations can beinitiated by said third memory store.
 7. A control apparatus for usewith a machine for folding a flat workpiece which includes conveyormeans for carrying a flat workpiece between a sensing station and afolding station, the control apparatus comprising, a detector andtransmitter means including a feeler switch, a toothed wheel and aphotocell for detectiNg and transmitting the length of a workpiece as ittravels on the conveyor means and for transmitting a signalcorresponding to the length of the workpiece, a pulse-shaping circuitmeans for receiving a signal from said detector and transmitter means,and R-C memory storage means for receiving a signal from saidpulse-shaping circuit means, a second capacitor, a switch means fortransferring at least part of said signal from capacitor, firstcapacitor to said second capacitor, a second transmitter means includingrotatable shaft operatively connected to said conveyor means to transmitto said second capacitor a further and cumulative signal correspondingto part of the length of said workpiece after the workpiece has leftsaid sensing station, and means including said second capacitor forinitiating a folding operation on the workpiece when the workpiece is inproper position at the folding station.
 8. A control apparatus asdefined in claim 7 further including means for discharging said firstcapacitor after said part of said signal is transferred from said firstcapacitor to said second capacitor for permitting said first capacitorto receive subsequent signals from said pulse-shaping circuit inresponse to the passage of a subsequent workpiece by said sensingstation.